1. Field of the Invention
Embodiments relate to switching DC-DC power converters including adaptive-minimum-on-time control and methods of adaptively controlling minimum-on-time for switching DC-DC power converters. More particularly, embodiments relate to switching DC-DC power converters including adaptive-minimum-on-time control and methods of adaptively controlling minimum-on-time of switching DC-DC converters, which may enable a reduction in switching loss by adaptively controlling a duty cycle of a power switch thereof based on, e.g., a magnitude of an input (or output) voltage.
2. Description of the Related Art
Switching DC-DC power converters, e.g., buck converters, may be employed in various electronic devices, e.g., mobile phones, laptop computers, etc., which receive power from a voltage source, e.g., a battery. Such electronic devices may include a plurality of circuits, e.g., an encoder, a decoder, a memory, a processor, etc., each of which may require a different voltage level than a voltage level supplied from a battery of the electronic device, and thus, DC-DC power converters may be employed to generate multiple controlled voltages from the single battery voltage.
A DC-DC converter may accept an input DC voltage Vin and may generate an output DC voltage Vo by, e.g., controllably storing energy in a component(s), e.g., a magnetic component such as an inductor. The amount of energy stored in the component(s) may be controlled by adjusting a duty cycle (ratio of on/off time) of, e.g., a power switch (e.g., two transistors connected in series between a first voltage source and a second voltage source) through which current and/or voltage is supplied. Accordingly, an output voltage Vo of a DC-DC converter is generally based on at least the input DC voltage Vin and the duty cycle of the transistors of the power switch, i.e., an amount of time the respective transistors are on and a number of times of the power switch is switched on and off.
In known devices, a minimum on-time of the power switch is set based on a maximum voltage of the battery of the electronic device. However, characteristics of the input DC voltage Vin supplied from a battery of the electronic device may change, e.g., decrease, over time. Therefore, in such known DC-DC converters efficiency thereof may decrease over time as the input DC voltage Vin supplied thereto decreases.
Further, with regard to the duty cycle of the power switch, some power is generally lost during operation of a switch. Power loss generally corresponds to a sum of conduction loss and switching loss. Conduction loss is generally proportional to a magnitude of output current, while switching loss is generally proportional to a number of switching times of the power switch. More particularly, power switching loss Psw may be represented by Equation 1:Psw=CV2f  (Equation 1)where C is parasitic capacitance of transistor(s) of the power switch, V is the charged voltage of the parasitic capacitance C, and f is the number of switching times for generating a desired output voltage Vo (or current).
Accordingly, it is desirable to provide a DC-DC converter that adaptively controls a minimum-on-time of the power switch in view of a change in the DC input voltage Vin and/or the power switching loss of the power switch.